New flavonoids and methylchromone isolated from the aerial parts of Baeckea frutescens and their inhibitory activities against cyclooxygenases-1 and -2

Abstract

In the present study, we carried out a phytochemical investigation of the ethanol extract of the aerial parts of Baeckea frutescens, which resulted in the isolation of two new flavonoid glycosides, myricetin 3-O-(5″-O-galloyl)-α-L-arabinofuranoside (1), 6-methylquercetin 7-O-β-D-glucopyranoside (2), one new methylchromone glycoside, 7-O-(4', 6'-digalloyl)-β-D-glucopyranosyl-5-hydroxy-2-methylchromone (3), together with three known compounds (4-6). The structures of these isolated compounds were established on the basis of 1D and 2D NMR techniques and chemical methods. The anti-inflammatory activities of the compounds 1-6 were evaluated for their inhibitory effects against cyclooxygenases-1 and -2 in vitro. Compounds 1-6 showed potent COX-1 and COX-2 inhibiting activities in vitro with IC₅₀ values ranging from 1.95 to 5.54 μmol·L^-1 and ranging from 1.01 to 2.27 μmol·L^-1, respectively.

Keywords: Baeckea frutescens; Cyclooxygenase-1; Cyclooxygenase-2; Flavonoid; Methylchromone.